by Karen Rustad; idea and some screenshots by Asheesh Laroia

The fourteen email clients, in order, are:

• pine
• Seamonkey
• SquirrelMail
• gnus
• Balsa
• K9
• YAM
• Sparrow
• elm
• Apple Mail
• Thunderbird
• Foxmail
• Mulberry
• mutt

All of the mail clients are named after various animal and plant species. Each screenshot has a letter (or short collection of letters) capitalized in its subject line. They also all have the same, Huffman-encoded string in the body of the email.

Arrange the mail clients on the tree at the top of the page based on their species / evolutionary history. This results in:

LR: pine
LLR: yam
LLLR: balsa
LLLLL: apple
LLLLRL: mulberry/elm
LLLLRR: elm/mulberry

RL: seamonkey
RRRR: Thunderbird/Sparrow
RRRL: Sparrow/Thunderbird
RRLR: SquirrelMail
RRLLR: gnus
RRLLLL: FoxMail
RRLLLRR: mutt/K9
RRLLLRL: K9/mutt

Assign the capitalized letters for each screenshot's subject line to the screenshot's branch on the tree, then interpret the Huffman-encoded string in the email bodies. This results in "THEMEDA TRIANDRA IN AU", which is a hint for the answer, KANGAROO GRASS.